Airflow generator and heat dissipation device incorporating the same

ABSTRACT

An airflow generator includes stacked airflow-generating units. Each airflow-generating unit includes a casing, first and second vibrating diaphragms received in the casing and spaced from each other, first and second driving members for driving the first and second vibrating diaphragms, and a nozzle connected to the casing. An inner space of the casing is divided into a first chamber formed between the first and second vibrating diaphragms, and a second chamber and a third chamber located at two opposite sides of the first chamber. The first driving member includes a first movable magnet attached to the first vibrating diaphragm, and a first stationary magnet received in the second chamber and attached to the casing. The second driving member includes a second movable magnet attached to the second vibrating diaphragm, and a second stationary magnet received in the third chamber and attached to the casing.

BACKGROUND

1. Technical Field

The disclosure generally relates to heat dissipation devices; and moreparticularly to a heat dissipation device incorporating an airflowgenerator.

2. Description of Related Art

With accelerated developments in the electronic information industries,electronic components such as central processing units (CPUs) ofcomputers are now capable of operating at much higher frequencies andspeeds. As a result, the heat generated by these CPUs during normaloperation is commensurately increased. If not quickly removed from theCPUs, this generated heat may cause them to become overheated andfinally affecting their workability and stability.

In order to remove the heat of the CPUs and hence enable the CPUs tocontinue normal operations, heat dissipation devices are provided todissipate heat of the CPUs. A conventional heat dissipation deviceincludes a fan, and a heat sink arranged at an outlet of the fan. Theheat sink is attached on a CPU or thermally connected to the CPU via aheat pipe. Heat generated by the CPU is transferred to a plurality offins of the heat sink. Airflow produced by the fan flows towards thefins of the heat sink to dissipate heat of the CPU to the outsideenvironment, and thus maintains the stability and normal operations ofthe CPU.

However, when the fan runs at a higher speed, the fan exhibits anoticeable noise. Furthermore, an impeller of the fan usually occupies alarger volume, which increases the size of the heat dissipation device.Therefore, this goes against the need for requiring more compact size inelectronic products.

What is needed, therefore, is a heat dissipation device to overcome theabove-described limitations.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the present embodiments can be better understood withreference to the following drawings. The components in the drawings arenot necessarily drawn to scale, the emphasis instead being placed uponclearly illustrating the principles of the present embodiments.Moreover, in the drawings, like reference numerals designatecorresponding parts throughout the several views.

FIG. 1 is an isometric, assembled view of a heat dissipation device inaccordance with an exemplary embodiment of the present disclosure.

FIG. 2 is an exploded view of the heat dissipation device of FIG. 1.

FIG. 3 is similar to FIG. 2, but viewed from a different aspect.

FIG. 4 is a cross-sectional view of the heat dissipation device of FIG.1, taken along a line IV-IV thereof.

FIG. 5 is a view schematically showing a first stage of an operationprocess of the heat dissipation device of FIG. 1.

FIG. 6 is similar to FIG. 5, showing a second stage of the operationprocess of the heat dissipation device of FIG. 1.

FIG. 7 is similar to FIG. 5, showing a third stage of the operationprocess of the heat dissipation device of FIG. 1.

FIG. 8 is an isometric, assembled view of a heat dissipation device inaccordance with a second embodiment of the present disclosure.

DETAILED DESCRIPTION

Referring to FIGS. 1-3, a heat dissipation device 100 according to anexemplary embodiment of the present disclosure is shown. The heatdissipation device 100 includes an airflow generator 10 and a heat sink20.

Referring also to FIG. 4, the airflow generator 10 includes a shell 11and a plurality of airflow-generating units 12. The airflow-generatingunits 12 are arranged in the shell 11, and are stacked together along ahorizontal direction. Each airflow-generating unit 12 includes a casing120, a first vibrating diaphragm 121, a second vibrating diaphragm 122,a first driving member 13, a second driving member 14, and a nozzle 123.

The casing 120 has a cuboid shape. The first and second vibratingdiaphragms 121, 122 are horizontally mounted in the casing 120 atdifferent levels. The first and second vibrating diaphragms 121, 122 arespaced from and parallel to each other. An inner space of the casing 120is divided into three chambers by using the first and second vibratingdiaphragms 121, 122; i.e., a first chamber 124 is formed between thefirst and second vibrating diaphragms 121, 122, a second chamber 125located above the first chamber 124 and isolated from the first chamber124 is formed by the first vibrating diaphragm 121, and a third chamber126 located below the first chamber 124 and isolated from the firstchamber 124 is formed by the second vibrating diaphragm 122. The firstvibrating diaphragm 121 and the second vibrating diaphragm 122 arespaced apart by a first distance H1. Each of the first and secondvibrating diaphragms 121, 122 is made of elastic material, such asrubber, flexible resin or a thin metal sheet.

The first driving member 13 is received in the second chamber 125 of thecasing 120, and includes a first movable magnet 131 and a firststationary magnet 132. The first movable magnet 131 is attached to amiddle of a top surface of the first vibrating diaphragm 121. The firststationary magnet 132 is attached to an inner surface of a top wall ofthe casing 120. The first movable magnet 131 and the first stationarymagnet 132 face each other, and are spaced apart by a second distanceH2. The second distance H2 is shorter than the first distance H1 betweenthe first and second vibrating diaphragms 121, 122.

The second driving member 14 is received in the third chamber 126 of thecasing 120, and includes a second movable magnet 141 and a secondstationary magnet 142. The second movable magnet 141 is attached to amiddle of a bottom surface of the second vibrating diaphragm 122. Thesecond stationary magnet 142 is attached to an inner surface of a bottomwall of the casing 120. The second movable magnet 141 and the secondstationary magnet 142 face each other, and are spaced apart by a thirddistance H3. The third distance H3 is substantially equal to the seconddistance H2 between the first movable magnet 131 and the firststationary magnet 132, and is shorter than the first distance H1 betweenthe first and second vibrating diaphragms 121, 122.

In this embodiment, both the first movable magnet 131 of the firstdriving member 13 and the second movable magnet 141 of the seconddriving member 14 are electromagnets, and both the first stationarymagnet 132 of the first driving member 13 and the second stationarymagnet 142 of the second driving member 14 are permanent magnets. Thefirst movable magnet 131 includes a movable iron core 1311 (comprising ashape of a thin piece) and a wire coil 1312 disposed around the movableiron core 1311. The movable iron core 1311 is made of a material whichcan be easily magnetized and demagnetized, such as soft iron or siliconsteel. The wire coil 1312 is attached on the first vibrating diaphragm121 and surrounds the iron core 1311. Alternatively, the wire coil 1312can be directly wound on and around the iron core 1311. The secondmovable magnet 141 includes a movable iron core 1411 and a wire coil1412 disposed around the iron core 1411. The iron core 1411 is made of amaterial which can be easily magnetized and demagnetized, such as softiron or silicon steel. The wire coil 1412 is attached on the secondvibrating diaphragm 122 and surrounds the iron core 1411. Alternatively,the wire coil 1412 can be directly wound on and around the iron core1411. A plurality of through holes (not labeled) are defined in asidewall of the casing 120 of each airflow-generating unit 12 forfacilitating the extension of an electric wire 127 therethrough toconnect the wire coils 1312 of the first movable magnets 131 of adjacentairflow-generating units 12 and for facilitating the extension of anelectric wire 128 therethrough to connect the wire coils 1412 of thesecond movable magnets 141 of adjacent airflow-generating units 12. Whenthe airflow-generating units 12 are assembled together, the wire coils1312 of the first movable magnets 131 of the airflow-generating units 12are connected to each other in series via the electric wires 127, andthe wire coils 1412 of the second movable magnets 141 of theairflow-generating units 12 are connected to each other in series viathe electric wires 128. Both the wire coils 1312 of the first movablemagnets 131 and the wire coils 1412 of the second movable magnets 141 ofthe airflow-generating units 12 are connected to an external powersupply (not shown).

The nozzle 123 is disposed at a lateral side of the casing 120 facingthe heat sink 20. The nozzle 123 is connected to a middle portion of thesidewall of the casing 120 corresponding to the first chamber 124. Thenozzle 123 defines a tapered air channel 1231 therein. A larger end ofthe air channel 1231 communicates with the first chamber 124, and asmaller end of the air channel 1231 faces the heat sink 20.

The shell 11 defines a receiving room (not labeled) therein with anopening 111 thereof facing the heat sink 20. The stackedairflow-generating units 12 are arranged into the shell 11 via theopening 111. The shell 11 is used for fixing the stackedairflow-generating units 12 together. In another embodiment, the stackedairflow-generating units 12 can be fixed together by adhesive or glue.

The heat sink 20 includes a plurality of spaced fins 21. A plurality ofair passages 22 are formed between adjacent fins 21. The airflowgenerator 10 is arranged at a lateral side of the heat sink 20, with thenozzles 123 of the airflow-generating units 12 facing the air passages22 of the heat sink 20. The smaller end of the nozzle 123 of eachairflow-generating unit 12 is spaced from an entrance of a correspondingair passage 22 of the heat sink 20 by a predetermined distance.

In operation of each airflow-generating unit 12, the external powersupply provides an alternating current to the wire coil 1312 of thefirst movable magnet 131 of the first driving member 13 and the wirecoil 1412 of the second movable magnet 141 of the second driving member14 of the airflow-generating unit 12 via the wires 127, 128. When acurrent is passed through the wire coil 1312 of the first movable magnet131 of the first driving member 13, the iron core 1311 of the firstmovable magnet 131 is magnetized to create a large magnetic field thatextends into the space around the iron core 1311. Similarly, when acurrent is passed through the wire coil 1412 of the second movablemagnet 141 of the second driving member 14, the iron core 1411 of thesecond movable magnet 141 is magnetized to create a large magnetic fieldthat extends into the space around the iron core 1411. The polarities ofthe magnetized first and second movable magnets 131, 141 are determinedby the direction of the current flowing through the wire coils 1312,1412. The magnetized first movable magnet 131 and the first stationarymagnet 132 of the first driving member 13 mutually attract or repel eachother alternately, and the magnetized second movable magnet 141 and thesecond stationary magnet 142 of the second driving member 14 alsomutually attract or repel each other alternately, thereby causing thefirst and second vibrating diaphragms 121, 122 to move towards eachother or away from each other simultaneously with the first and secondmovable magnets 131, 141. When the first and second driving members 13,14 drive the first and second vibrating diaphragms 121, 122 to movetowards each other simultaneously, the first and second vibratingdiaphragms 121, 122 compress the air inside the first chamber 124 tomove towards the air channel 1231 of the nozzle 123, thereby generatingan airflow jetting towards the air passages 22 of the heat sink 20 fromthe smaller end of the nozzle 123. The airflow then flows along the airpassages 22 of the heat sink 20 to take away the heat transferred to thefins 21.

Referring to FIGS. 5-7, an airflow-generating process of eachairflow-generating unit 12 in one generating period is described indetail as follows.

The airflow-generating process is divided into three stages. During thefirst stage of the airflow-generating process, the external power supplyprovides a negative/positive current to the wire coil 1312 of the firstmovable magnet 131 to magnetize the iron core 1311 of the first movablemagnet 131. The iron core 1311 then becomes magnetized. An end of themagnetized iron core 1311 adjacent to the first stationary magnet 132has a magnetic polarity the same as that of an end of the firststationary magnet 132 adjacent to the magnetized iron core 1311. Themagnetized iron core 1311 of the first movable magnet 131 is therebyrepelled by the first stationary magnet 132, thus driving the firstvibrating diaphragm 121 to move towards the second vibrating diaphragm122 with the magnetized iron core 1311. At the same time, the externalpower supply provides a negative/positive current to the wire coil 1412of the second movable magnet 141 to magnetize the iron core 1411 of thesecond movable magnet 141. The iron core 1411 then becomes magnetized.An end of the magnetized iron core 1411 adjacent to the secondstationary magnet 142 has a magnetic polarity the same as that of an endof the second stationary magnet 142 adjacent to the magnetized iron core1411. The magnetized iron core 1411 of the second movable magnet 141 isrepelled by the second stationary magnet 142, thus driving the secondvibrating diaphragm 122 to move towards the first vibrating diaphragm121 with the magnetized iron core 1311. In other words, the first andsecond driving members 13, 14 drive both the first and second vibratingdiaphragms 121, 122 to move towards each other during the first stage ofthe airflow-generating process. Thus, the air in the first chamber 124is compressed by the first and second vibrating diaphragms 121, 122 tomove towards the air channel 1231 of the nozzle 123.

Referring to FIG. 5, when the first and second vibrating diaphragms 121,122 move from their originally horizontal positions to a plurality ofcurved positions or contours as indicated by a plurality of broken lines121 a, 122 a, a first airflow 31 is generated and jets towards the airpassages 22 of the heat sink 20 from the outer end of the nozzle 123having a high flow speed. The first airflow 31 flows forward along theair passages 22 of the heat sink 20 and exchanges heat with the fins 21to take away the heat transferred to the fins 21.

Then the negative/positive current supplied to the wire coil 1312 of thefirst movable magnet 131 reverses current direction to change to apositive/negative current, thereby entering the second stage of theairflow-generating process. When the iron core 1311 is magnetized by thereversed positive/negative current, the end of the magnetized iron core1311 adjacent to the first stationary magnet 132 has a magnetic polarityopposite to that of the end of the first stationary magnet 132 adjacentto the magnetized iron core 1311. The magnetized iron core 1311 of thefirst movable magnet 131 is attracted by the first stationary magnet132, thereby driving the first vibrating diaphragm 121 to move away fromthe second vibrating diaphragm 122 together with the magnetized ironcore 1311. At the same time, the negative/positive current supplied tothe wire coil 1412 of the second movable magnet 141 also reversesdirection to change to the positive/negative current. When the iron core1411 is magnetized by the reversed positive/negative current, the end ofthe magnetized iron core 1411 adjacent to the second stationary magnet142 has a magnetic polarity opposite to that of an end of the secondstationary magnet 142 adjacent to the magnetized iron core 1411. Themagnetized iron core 1411 of the second movable magnet 141 is thenrepelled by the second stationary magnet 142, thereby driving the secondvibrating diaphragm 122 to move away from the first vibrating diaphragm121 together with the magnetized iron core 1411. In other words, thefirst and second driving members 13, 14 drive the first and secondvibrating diaphragms 121, 122 to move away from each other during thesecond stage of the airflow-generating process.

Referring to FIG. 6, when the first and second vibrating diaphragms 121,122 move from their curved positions as indicated by the broken lines121 a, 122 a (see in FIG. 5) back to their original horizontalpositions, the air outside and around the nozzle 123 is sucked into theair passages 22 of the heat sink 20, thereby forming a second airflow 32flowing forward along the air passages 22 of the heat sink 20.Particularly, the second airflow 32 has a flow rate ten times as largeas the first airflow 31.

After the first and second vibrating diaphragms 121, 122 have moved backto their horizontal positions, the third stage of the airflow-generatingprocess then begins as follow. Referring to FIG. 7, the first and secondvibrating diaphragms 121, 122 continue to move away from each otheruntil the first and second vibrating diaphragms 121, 122 reach theircurved positions as indicated by the broken lines 121 b, 122 b. Duringthe third stage of the airflow-generating process, a volume of the firstchamber 124 is expanded, thereby allowing the cool air (indicated by aplurality of arrows 33) outside and around the nozzle 123 to be suckedinto the first chamber 124 of the casing 120 for a subsequentairflow-generating process. Then the positive/negative current suppliedto the wire coils 1312, 1412 of the first and second movable magnets131, 141 reverse current direction to change to a negative/positivecurrent, thereby entering the first stage of the subsequentairflow-generating process.

In each airflow-generating unit 12, the first distance H1 between thefirst and second vibrating diaphragms 121, 122 is properly over twotimes longer than the second distance H2 between the first movablemagnet 131 and the first stationary magnet 132, thereby reducing theinteraction between the first movable magnet 131 of the first drivingmember 13 and the second driving member 14. Similarly, the firstdistance H1 between the first and second vibrating diaphragms 121, 122is properly over two times longer than the third distance H3 between thesecond movable magnet 141 and the second stationary magnet 142, therebyreducing the interaction between the second movable magnet 141 of thesecond driving member 14 and the first driving member 13.

In the airflow-generating process of each airflow-generating unit 12,the external power supply can provide a pulse current to the wire coils1312, 1412 of the first and second movable magnets 131, 141. In suchcircumstances, the current supplied to the wire coils 1312, 1412 of thefirst and second movable magnets 131, 141 is zero during the second andthird stages of the airflow-generating process.

In each airflow-generating unit 12, by exchanging the positions of thefirst movable magnet 131 and the first stationary magnet 132 of thefirst driving member 13, and maintaining the positions of the secondmovable magnet 141 and the second stationary magnet 142 of the seconddriving member 14 unchanged, the airflow-generating unit 12 can alsoachieve the above airflow-generating process. By exchanging thepositions of the second movable magnet 141 and the second stationarymagnet 142 of the second driving member 14, and maintaining thepositions of the first movable magnet 131 and the first stationarymagnet 132 of the first driving member 13 unchanged, theairflow-generating unit 12 can also achieve the above airflow-generatingprocess. By exchanging or switching the positions of the first movablemagnet 131 and the first stationary magnet 132 of the first drivingmember 13, and exchanging or switching the positions of the secondmovable magnet 141 and the second stationary magnet 142 of the seconddriving member 14, the airflow-generating unit 12 can also achieve theabove airflow-generating process.

In each airflow-generating unit 12, under the alternating current, thefirst and second driving member 13, 14 drive the first and secondvibrating diaphragms 121, 122 to periodically compress the air insidethe first chamber 124 of the casing 120, thereby periodically generatingan airflow jetting towards the air passages 22 of the heat sink 20 fromthe outer end of the nozzle 123. By supplying alternating currents ofdifferent frequencies, the flow rate of the airflow generated by theairflow-generating unit 12 can be adjusted to meet different coolingrequirements.

Further, a first electromagnetic interference (EMI) shielding layer 1251is formed on an inner surface of the casing 120 and the bottom surfaceof the first vibrating diaphragm 121, and encircles the second chamber125. The first EMI shielding layer 1251 encloses the first drivingmember 13 therein, thereby preventing EMI radiation from the firstmovable magnet 131 of the first driving member 13 to interact with theelectronic components outside the shell 11 of the air airflow generator10. A second electromagnetic interference (EMI) shielding layer 1261 isformed on the inner surface of the casing 120 and the bottom surface ofthe second vibrating diaphragm 122, and encircles the third chamber 126.The second EMI shielding layer 1261 encloses the second driving member14 therein, thereby preventing EMI radiation from the second movablemagnet 141 of the second driving member 14 to interact with theelectronic components outside the shell 11 of the air airflow generator10.

In the heat dissipation device 100, the heat transferred to the fins 21of the heat sink 20 is dissipated by the airflow generator 10. Thenumber of airflow-generating units 12 of the airflow generator 10 foractual implementation can be chosen so as to meet the specific coolingrequirements. Further, no motor and impeller are used in the heatdissipation device 100, thus the heat dissipation device 100 can have asmaller size, and a quieter working environment is obtained.

Referring to FIG. 8, a heat dissipation device 100 a according to asecond embodiment is illustrated. Comparing with the heat dissipationdevice 100 illustrated in FIGS. 1-4, this heat dissipation device 100has an additional airflow generator 10 a. In other words, the heatdissipation device 100 of the second embodiment includes the heat sink20, the airflow generator 10 and the airflow generator 10 a. The airflowgenerator 10 a has a conformation or structure the same as the airflowgenerator 10, and includes a plurality of stacked airflow-generatingunits 12. The airflow generator 10 a is arranged at a side of theairflow generator 10 which sits opposite to the heat sink 20, with thenozzle 123 of each airflow-generating unit 12 thereof pointing in adirection opposite to the nozzle 123 of each airflow-generating unit 12of the airflow generator 10.

It is to be understood, however, that even though numerouscharacteristics and advantages of the present embodiments have been setforth in the foregoing description, together with details of thestructures and functions of the embodiments, the disclosure isillustrative only, and changes may be made in detail, especially inmatters of shape, size, and arrangement of parts within the principlesof the disclosure to the full extent indicated by the broad generalmeaning of the terms in which the appended claims are expressed.

1. An airflow generator, comprising: at least one airflow-generatingunit, comprising: a casing; a first and a second vibrating diaphragmsreceived in the casing and spaced from each other, an inner space of thecasing being divided into a first chamber formed between the first andsecond vibrating diaphragms, and a second chamber and a third chamberlocated at two opposite sides of the first chamber, the second chamberand the third chamber being isolated from the first chamber by the firstand second vibrating diaphragms, respectively; a nozzle connected to asidewall of the casing and located at a position corresponding to thefirst chamber, an air channel being defined in the nozzle andcommunicating the first chamber with an outer environment; a firstdriving member adapted for driving the first vibrating diaphragm, thefirst driving member comprising a first movable magnet attached to thefirst vibrating diaphragm, and a first stationary magnet received in thesecond chamber and attached to the casing at a position corresponding tothe first movable magnet; and a second driving member adapted fordriving the second vibrating diaphragm, the second driving membercomprising a second movable magnet attached to the second vibratingdiaphragm, and a second stationary magnet received in the third chamberand attached to the casing at a position corresponding to the secondmovable magnet; wherein when the first and second driving members drivethe first and second vibrating diaphragms to move towards each other,the first and second vibrating diaphragms compress the air inside thefirst chamber of the casing to move towards the air channel of thenozzle, thereby generating an airflow jetting to the outer environmentthrough the nozzle.
 2. The airflow generator of claim 1, wherein one ofthe first movable magnet and the first stationary magnet of the firstdriving member is a permanent magnet, the other one of the first movablemagnet and the first stationary magnet of the first driving member is anelectromagnet, one of the second movable magnet and the secondstationary magnet of the second driving member is a permanent magnet,the other one of the second movable magnet and the second stationarymagnet of the second driving member is an electromagnet.
 3. The airflowgenerator of claim 2, wherein the first and second movable magnets areelectromagnets, and the first and second stationary magnets arepermanent magnets.
 4. The airflow generator of claim 3, wherein thefirst movable magnet comprises a movable iron core and a wire coildisposed around the iron core.
 5. The airflow generator of claim 3,wherein the second movable magnet comprises a movable iron core and awire coil disposed around the iron core.
 6. The airflow generator ofclaim 1, wherein the first and second vibrating diaphragms are parallelto each other, the first vibrating diaphragm and the second vibratingdiaphragm being spaced apart by a first distance, the first movablemagnet and the first stationary magnet being spaced apart by a seconddistance, the second movable magnet and the second stationary magnetbeing spaced apart by a third distance, and both the second distance andthe third distance being shorter than the first distance, respectively.7. The airflow generator of claim 1, wherein a first electromagneticinterference shielding layer and a second electromagnetic interferenceshielding layer are formed on the casing, and on the first and secondvibrating diaphragms, the first electromagnetic interference shieldinglayer encircles the second chamber, and the second electromagneticinterference shielding layer encircles the third chamber.
 8. The airflowgenerator of claim 1, wherein the first and second movable magnets areattached to the middle portions of the first and second vibratingdiaphragms, respectively.
 9. The airflow generator of claim 1, furthercomprising a shell, wherein the at least one airflow-generating unit ismounted in the shell.
 10. A heat dissipation device, comprising: a heatsink defining a plurality of air passages therein; and an airflowgenerator disposed at a side of the heat sink, the airflow generatorcomprising: a plurality of airflow-generating units stacked together,each of the airflow-generating units comprising: a casing; a first and asecond vibrating diaphragms received in the casing and spaced from eachother, an inner space of the casing being divided into a first chamberformed between the first and second vibrating diaphragms, and a secondchamber and a third chamber located at two opposite sides of the firstchamber, the second chamber and the third chamber being isolated fromthe first chamber by the first and second vibrating diaphragms,respectively; a nozzle connected to a sidewall of the casing and locatedat a position corresponding to the first chamber, an air channel beingdefined in the nozzle and communicating the first chamber with an outerenvironment; a first driving member adapted for driving the firstvibrating diaphragm, the first driving member comprising a first movablemagnet attached to the first vibrating diaphragm, and a first stationarymagnet received in the second chamber and attached to the casing at aposition corresponding to the first movable magnet; and a second drivingmember adapted for driving the second vibrating diaphragm, the seconddriving member comprising a second movable magnet attached to the secondvibrating diaphragm, and a second stationary magnet received in thethird chamber and attached to the casing at a position corresponding tothe second movable magnet; wherein when the first and second drivingmember drive the first and second vibrating diaphragms to move towardseach other, the first and second vibrating diaphragms compress the airinside the first chamber of the casing to move towards the air channelof the nozzle, thereby generating an airflow jetting towards the airpassages of the heat sink through the nozzle.
 11. The heat dissipationdevice of claim 10, wherein one of the first movable magnet and thefirst stationary magnet of the first driving member is a permanentmagnet, the other one of the first movable magnet and the firststationary magnet of the first driving member is an electromagnet, oneof the second movable magnet and the second stationary magnet of thesecond driving member is a permanent magnet, the other one of the secondmovable magnet and the second stationary magnet of the second drivingmember is an electromagnet.
 12. The heat dissipation device of claim 11,wherein the first and second movable magnets are electromagnets, and thefirst and second stationary magnets are permanent magnets.
 13. The heatdissipation device of claim 12, wherein the first movable magnetcomprises a movable iron core and a wire coil disposed around the ironcore.
 14. The heat dissipation device of claim 12, wherein the secondmovable magnet comprises a movable iron core and a wire coil disposedaround the iron core.
 15. The heat dissipation device of claim 10,wherein the first and second vibrating diaphragms are parallel to eachother, the first vibrating diaphragm and the second vibrating diaphragmbeing spaced apart by a first distance, the first movable magnet and thefirst stationary magnet being spaced apart by a second distance, thesecond movable magnet and the second stationary magnet being spacedapart by a third distance, and both the second distance and the thirddistance being shorter than the first distance, respectively.
 16. Theheat dissipation device of claim 10, wherein a first electromagneticinterference shielding layer and a second electromagnetic interferenceshielding layer are formed on the casing, and on the first and secondvibrating diaphragms, the first electromagnetic interference shieldinglayer encircles the second chamber, and the second electromagneticinterference shielding layer encircles the third chamber.
 17. The heatdissipation device of claim 10, wherein the first and second movablemagnets are attached to the middle portions of the first and secondvibrating diaphragms, respectively.
 18. The heat dissipation device ofclaim 10, wherein the airflow generator further comprises a shell, andthe airflow-generating units being mounted in the shell.
 19. The heatdissipation device of claim 10, further comprising an additional airflowgenerator, wherein the additional airflow having a conformation the sameas the airflow generator, the additional airflow generator beingarranged at a side of the airflow generator opposite to the heat sink,with the nozzle of each airflow-generating unit thereof pointing in adirection opposite to the nozzle of each airflow-generating unit of theairflow generator.